Images of the social and economic world

Here is an ordinary map of the world:

Click on image for a larger version

Roughly speaking, on a map like this, the sizes of the countries of the
world are in proportion to their actual sizes on the surface of the planet
and their shapes are the same as their actual shapes. (This is only
approximate though, since some distortion is inevitable when you go from a
spherical planet to a flat map.)

It's possible, however, and sometimes very useful, to redraw the map with
the sizes of countries made bigger or smaller in order to represent
something of interest. Such maps are called cartograms and can be
an effective and natural way of portraying geographic or social data.

Here, for example, is a cartogram that shows the human population of the
countries of the world:

Population

Click on image for a larger version

In this map the sizes of countries are proportional not to their actual
landmass but instead to the number of people living there; a country with
20 million people, for instance, appears twice as large as a country with
10 million.

Although the figures for populations of countries are well established and
familiar to many, the cartogram provides a new way of looking at them and
in particular makes clear the enormous disparity in the population of
different regions. Note how large India and China have become: between
them these two countries account for more than a third of the population of
the world. On the other hand, notice the near-disappearance of Canada and
Russia, the world's two largest countries by land area, which have
relatively few people in them.

Notice also how the lines of latitude and longitude have become distorted
by the growing and shrinking countries. This is an unavoidable consequence
of the cartogram transformation: in order to give the countries the right
sizes and still have them fit together you need to warp things a bit. The
method used here, however, does a pretty good job of keeping the map
recognizable.

Cartograms are most often used to show population data, but there is no
reason why they need be limited to population. They can in principle be
used to show almost any quantity. Here is a cartogram of the world in
which the sizes of countries are proportional to Gross Domestic Product,
which is a measure of how much wealth a country's economy generates, and
hence, to an extent, of the wealth of the country's inhabitants:

Gross domestic product

Click on image for a larger version

Notice how America and Europe dominate this map, along with Japan (yes
– that huge dark-green island on the right really is Japan), while
Africa dwindles almost to invisiblity.

Now here are a few more cartograms. In all of the maps on this page the
countries have the same colors, which helps to identify countries in the
cases where shapes have changed a lot.

Child mortality

Click on image for a larger version

People living with HIV/AIDS

Click on image for a larger version

Total spending on healthcare

Click on image for a larger version

Energy consumption (including oil)

Click on image for a larger version

Greenhouse gas emissions

Click on image for a larger version

If you are interested to see more cartograms, you might like to visit the
website of the Worldmapper
Project, where a group of colleagues and I are gathering together an
ever-growing collection of cartograms showing all sorts of aspects of the
social, economic, and geographic world. The web site contains, among other
things, downloadable posters of cartograms that you can print out, along
with data sets, descriptions of the statistical analyses, and information
about the methods used to produce the maps. (The maps shown here were made
specially for this page and are not part of the Worldmapper Project, but
there are similar maps on the project web site.)

Permission is hereby granted for the use and distribution by others of the
text and figures on this page for noncommercial purposes. Go ahead and
send them to your friends, post them on your blog, use them in school.
Whatever. My only request is that you either give a link to this page or
just mention that the maps were made by me. (Or both, if you're feeling
particularly enthusiastic.) If you would like to use any of these
materials for commercial purposes, please drop me a line. Contact details
are here.

If you spot any errors in the text or figures, the author would very much
appreciate hearing about it. Again, contact
details are here.

High-resolution versions of the figures are available on request from
the author.

My computer software for producing cartograms is freely available here. A number of other
programs implementing the cartogram algorithm of Gastner and Newman are
also available. See here,
here, and here.

The views expressed on this web page are personal and are not necessarily
shared by the University of Michigan.

Mark Newman, Department
of Physics and Center for the Study of Complex Systems, University of
Michigan
Email: mejn@umich.edu
Updated: April 22, 2009